I'm sure there's poisonous herbs out there, go eat some.
I can legally grow hundreds of herbs and flowers in my own garden all of which have an effect on the human body in one way or another. Many of these have medicinal properties. Some, which I am permitted to grow have portions that are deadly if ingested at all and others if in too high a quantity. Why is it that this particular herb which pre-existed this nation upon this land is so different that it falls under the jurisdiction of the commerce clause? And, moreover where is the power of the Federal Government enumerated in our Constitution to eradicate it and imprison its possessors, protectors, and propagators?